Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Contact Lens > test 1 > Flashcards

test 1 Flashcards

(100 cards)

Start Studying
1
Q

What are the 2 types of lenses?

A

Scleral and cornea l

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is a scleral lens?

A

a lens that is extends beyond the diameter of the cornea

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are some examples of a scleral lens?

A

soft lenses and haptic lens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what is a corneal lens?

A

a lens that is the same diameter as the cornea

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what is an example of a corneal lens?

A

rigid lenses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

how are corneal lenses supported?

A

with fluid retention AND OR the lid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

In what year and what concept did Leonardo Da Vinci come up with?

A

a very basic optical system where the cornea is neutralized through contact with an optical medium. 1508

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What did Rene Discartes come up with and when?

A

sketched an elongated tube filled with water and at the end had a glass the same shape as a cornea. 1636

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Thomas Young

A

understood how to neutralize cornea, but did not think of CLs. 1801

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Sir John F. W. Herschel

A

1823, described the elements of a CL more precisely but did not put into practice

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Adolf Fick

A

1888, A contact spectacle. Described the first contact lens with refractive power known to have actually been worn.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What was the very first contact lens?

A

a thin glass bowl invented by adolf fick in 1888. can wear it for 2 hrs without irritation but it had no power.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what was the second CL to be developed?

A

made with a glass blower. bi-curve lens of 14mm in diameter. This was used in irregular astigmats and they had visual improvement.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What were the first cosmetic lenses?

A

lenses painted with irises on them to avoid enucleating eye

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Eugene Kalt

A

1888, made the first CL to tx keratoconus. and first cosmetic lens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

August Muller

A

1889, structured lenses so that posterior surface could be held in place by cappillary attraction. anterior surface would correct refractive error. used cocaine as anesthesia. did fittings on himself to neutralize his -14.00 D myopia.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

who created the lift off on the cornea?

A

August muller because he saw that tears were important to prevent corneal edema.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Karl Zeiss

A
  1. Developed the first trial lens made of glass..was very heavy and not successful.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

spin casting

A

uses liquid polymer which is spun to create the correct curvature

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

cast molding

A

uses liquid polymer filled in a mold, most disposable lenses are cast in mold

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

lathe cutting

A

uses solid polymer that is cut and polished to the power required

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Muller Co.

A

made lenses from blown glass on individual basis in the presence of the patient in an attempt to correct his ocular irregularity. had smooth edges and regular curvature.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

ptosis crutch

A

ridges were upper eyelid can rest. caused DES bc patient had difficulty blinking.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

joseph dallos.

A

emphasized fitting lens with slight difference bw. lens and cornea to allow tears to flow unnderneath. noticed central cornea spherical and peripheral was flatter.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
william feimbloom
1936, the first to use plastic to capture the advantage of low specific gravity. hybrid lenses.
26
J. Teissler
1937, made corneo-scleral lenses shell from cellulose acetate plastic (first gas permeable lens)
27
Rhom and Haas Co.
1936, introduced to the US a transparant material known as PMMA
28
PMMA
dominated CL field for 4 decades.
29
John Mullen and Theodore Obrig
1938, developed techniques for making scleral lenses from PMMA (found CL could be made thinner but still had difficulty with oxygen delivery.
30
Kevin Tuohy
developed the first corneal CL that has became a practical device for correction. 1946, technician cut erroneously and created RGP. found these lenses eliminated the symptoms of halos.
31
George Butterfield
1950, – Recognized that by adding various peripheral curves to the posterior surface of the lens central curve could nearly match the radius of curvature of the cornea. • This represented the first introduction of the modern term of fitting “on K” or contouring the cornea.
32
Otto Wichterle
1952, synthesized HEMA, produced hydrogel lenses of different degrees of water content. in 1961, created more casting machines.
33
C lenses
first lenses introduced by B&L was barely successful.
34
N lenses
2nd lenses introduced by B&L, was significantly more popular.
35
what did Vistakon do?
introduced the first disposable lenses. (Acuvue)
36
Cellulose Acetate Butyrate
was gas permeable but poor physical stability and warped easily
37
Norman Gaylord
1971, invented silicone methacrylate RGP material. permeability was similar to CAB and it was more stable.
38
how did intro of fluoride help?
increased Dk of lens. FS/A
39
function of tear film?
maintain hydration of soft lenses and cornea. anterior refractive surface.
40
what is the most commonly used CL?
Silicone hydrogel
41
high wetting angle
the higher the angle, the less tearsthat is spread over surface
42
components of tear
Mucous (basal layer) Aqueous layer Lipid layer
43
what glands produce mucus in tears
goblet cells, glands of moll and krause
44
glands that produce aqueous layer in tears
lacrymal gland, accessory gland of zeiss
45
glands that produce lipid layer
meibomian glands. this prevents evaporation
46
what does TBUT measure?
mucus layer, when that evaporates, water touches cornea and cornea is hydrophobic and the water breaks.
47
what is n of cornea?
1.376 and power of 45D
48
what is the thickness of the cornea
0.52 in the center and 0.97 in periphery
49
5 layers of the cornea
``` epithelium with basement membrane bowman's zone stroma descemet's membrane endothelium ```
50
epithelium of cornea
50 um in thickness, 10% of total corneal thickness. 5-6 layers basal, wings and surface cells
51
glycocalyx
helps mucin to adhere to corneal epithelial cells.
52
how fast are small corneal abrasions healed?
24 hours
53
what attaches epithelium to basement?
hemidesmosomes
54
how long does basement take to heal?
months
55
what makes up 90% of corneal thickness?
bowman's zone (part of stroma)
56
descemet's membrane
is elastic but consists of collagen
57
to avoid corneal edema how should the lens be fitted?
1.50D flatter than the flattest corneal meridian
58
what percent of the stroma is water?
78%
59
how much of tears is NaCL?
.91%
60
When the eye is open, tear osmolarity is ______________ due to evaporation into the atmosphere.
higher
61
When the eyes are closed the tear osmolarity is ___________ and hence a slight corneal thickness is produced
lower
62
__________ use when corneal oxygen supply is deficient.
anaerobic glycolysis
63
________ used 15% of the glucose in the cornea but produces three times the total corneal energy.
aerobic glycolysis
64
56. During sleep, the oxygen supply to the cornea comes from the
palpebral conjunctiva
65
57. _____________ is the primary source of oxygen in the endothelium
aqueous humor
66
58. At 0% of oxygen level the cornea swells 8% in 3 hours.
this is maximum corneal swelling
67
59. A contact lens worn overnight, under experimental extended wear conditions, show a corneal swelling of about
12- 13 %
68
60. Low transmissibility lenses provide an additional ____________ oxygen from transmission, which in most patients reduces any corneal swelling to less than 1%.
3-6 %
69
61. Medium transmissibility lenses provide oxygen levels of ____________ and eliminate clinical edema in daily wear patients
5-8%
70
62. High transmissibility lenses provide levels of ______________.
8 - 16%
71
63. A practical clinical description of the oxygen tension produced in the pre-corneal film by transmission through a contact lens
Equivalent oxygen percentage
72
64. Which of the following material has the ability to transmit and increase oxygen level in the cornea?
silicone
73
65. It’s termed the permeability of a contact lens material. It is an intrinsic characteristic of the material which is not related to its thickness.
Dk value
74
is termed the lens oxygen transmissibility. This measure is inversely proportional to lens thickness.
Dk/t
75
Low transmission material cause a corneal swelling of ______.
6- 8 %
76
Medium transmission material cause a corneal swelling of ______
2-4 %
77
High transmission material cause a corneal swelling of ______.
0-2%
78
9. Developed with optical power with the help of a glass blower. Bi curve lens of 14mm in diameter. Was tried in 6 patients with irregular astigmatism due to scaring.
second lens
79
A thin, glass bowl, was worn for 2 hours, the shell stabilized well but had no power.
first lens
80
previous tx of keratoconus was
d. Cauterization of cone with silver nitrate, instillation of myotics and application of pressure dressing.
81
Dk/t
D= diffusion k= solubility t= thickness minimum is 24
82
F1
front surface power (n'-n)/ r1
83
F2
back surface power (n-n')/ r2
84
Fv
front vertex power | [F2/1- (t/n)(f2)] + F1
85
Fv'
back vertex power | [F1/ 1-(t/n)(F1)] + F2
86
F1 with F2 and Fv' given
(Fv' - F2) / 1 + (t/n) (Fv' - F2)
87
n of a keratometer
337.5
88
plus lenticular
for negative power lenses greater the 5.00 D it minimizes problems associated with thick edges.
89
minus lenticular
used to increase edge thickness in plus lenses and minus lenses up to -1.50 D
90
what effect does a spectacle corrected myope have?
Bi object appears further away
91
what effect does a spectacle corrected hyperope have?
bo, objects appear closer
92
who has more complaints with CLs at near?
exo myopes and eso hyperopes
93
Effective power
Ep= Fv’/1-d(Fv’)
94
Vergence F
(100/l) + Fv'
95
EpV effective power vergence
= VerF/ 1-d(VerF)
96
accommodation
EpV- Ep
97
how to calculate accommodation with spectacles?
1st calculate d 2nd: Ep 3: VeF 4: EpV 5: EpV - Ep
98
How to calculate accommodation in CLs
1st: now, lens is at cornea plane so distance of object is l+vd Ex. L=40cm, VD=12mm so new distance is 41.2cm 2nd: calculate power of the CL at the corneal plane (Epcp) using just the vertex distance 3rd: calculate vergence power leaving CL 4th: calculate the effective power of that vergence at the principle plane 5th: calculate accommodation, where Epv-Ep (Ep, as in what was calculated for spectacles (at the principle plane) using d)
99
mag of spectacle wearing hyperopic aphakic patient
50-60%
100
mag of CL wearing hyperope aphakic patient
3%

Contact Lens (1 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions