monocular perception of depth

1> over lapping contours
2> realtive size of ibjects
3> aerial perspective
4> linear perspective
5> light and shade
6> movement parallax
7> accomodation effort

A CONSTANT FOR DIFFERENT IOL

appaswami ( APPA)
5.25 mm- 118.4(phaco)
6.5mm-    118.2(ECCE)
fold    -     118(phaco)
6mm -     115.3(anterior chamber IOL- roughly deduct 3 from calculated PCIOL power)

acry
IQ-118.7
single piece(SP), multipiece(MP)-118.4
TECHNISZA-119.1
SENSUR ACRYLIC- 118.4
B&L ACRYLIC- 118
ACREOS AO- 118
RESTORE- 118.9

power calculation of intra ocular lens (IOL)

SANDERS, RETZLAFF, KRAFF ( SRK)  FORMULA FOR IOL POWER CALCULATION-
IOL power(P) = A  - 2.5*AL  -0.9*Km
A=(SPECIFIC CONSTANT )
AL= (AXIAL LENGTH IN MILIMETERS)
Km=(CORNEAL POWER IN DIOPTRES-  TAKE THEIR AVERAGE OF 2 MERIDIANS , normal values 43-46.5D average 44D )

REPEAT  BIOMETRY(AL, Km)- if their is difference >=0.3 mm in AL of rt and lt eyes, >=1.5D difference in Km values of 2 meridians
APPLIED WHEN AL IS 22-24.5 mm

SRK 2 FORMULA- replace  A constant  by-
AL <20           :        A+3
AL= 20-20.99 :         A+2
AL=21-21.99  :         A+1
AL=22-24.5   :          A
AL> 24.5       :          A-0.5

MODIFIED SRK 2 FORMULA-
IF
AL <20 : A+1.5
AL 20-21: A+ 1
AL 21-22: A+0.5
AL 22-24.5: A
AL 24.5-26 : A-1
AL>26      : A-1.5

LASER IN DIABETIC MACULOPATHY

INDICATION-

all eyes with clinically significant macular edema irrespective of level of visual acuity as it reduces the risk for visual loss by 50%

CONTRAINDICATION-

severe ischaemic maculopathy

FOCAL LASER-

deliver burns to microaneurysm or at centre of ring of exudates

500 -3000 micron from centre of macula (upto 300 micron may be needed if CSME persists despite previous treatment and visual acuity is less than 6/12, exposure is .05 s)

spot size - 50-100 micron

exposure .1s

power sufficient to obtain gentle whitening or darkening of the lesions

MACULAR GRID-

500 micron from centre of macula, and 500 micron from temporal margin of disc

spot size 100 micron

exposure time .1 s

light intensity burn

ARTERIOVENOUS CROSSING CHANGES IN HYPERTENSION

AV nicking (GUNN SIGN): hourglass constrictions of vein on both sides of the crossing and aneurysmal-like swellings.

BONNET'S SIGN-
banking of vein where it appears dilated distal to crossing

SALUS SIGN-

Sclerosis may shorten or elongate retinal arterioles with the branches coming off at right angles. This change in length deflects the veins at the common sheath and changes the course of the vein

Right angled deflection of vein which gives the vein a S shaped bend

grading of hypertensive retinopathy

KEITH- WAGNER -BARKER CLASSIFICATION 1939-

-based on retinal changes in known grade of HYPERTENSION

GROUP I

-mild HTN

-minimal constriction of retinal arteroles<generalised>

-some tortuosity of retinal arteroles

GROUP II

-minimal or no other systemic involvement

-I +

-more definite focal narrowing

-arteriovenous nicking

GROUP III

-identifiable cardiac , cerebral , or renal dysfunction

-I+ II+

-hemorrhages

-exudates

-vasospastic changes

-cotton wool spot

GROUP IV

-more severe cardiac , cerebral , or renal dysfunction

-optic disc edema (v/s papilloedema from raised ICT - presence of cotton wool spot etc)

-ELSCHNIG'S SPOTS

SCHIE'S CLASSIFICATION OF HYPERTENSIVE RETINOPATHY 1953-

CHANGES OF HTN -

stage 0-

no visible vascular abmormality

stage I-

diffuse arteriolar narowing esp in smaller vessels

uniform arteriolar calibre ,no focal constriction

stage II-

more pronounced arteriolar narrowing

focal arteriolar attenuation

stage III-

I + II +
hemorrhages

stage IV-

retinal edema

hard exudates

optic disc edema

ARTERIOLOSCLEROTIC CHANGES-

stage 0 -

normal

stage 1-

broadened arteteriolar light reflex

minimal or no arteriovenous compression

stage2-

1+

more prominent crossing changes

stage 3-

1+2+

copper wire appearance

more av compression

stage 4-

silver wire appearance

crossing changes most severe

seven rings of blunt trauma to eye

seven rings of blunt trauma to eye
1> sphincter pupillae - sphincter tear

2> the iris base - iridodialysis

3> anterior ciliary body -angle recession (longitudinal tear of ciliary body face splitting circular fibres from longitudinal fibres of ciliary body)

commonest source of hyphaema
marked posterior displacement of the iris & wide ciliary body band posterior to the scleral spur
glaucoma is not due to recession per se but due to collateral damage to trabecular meshwork
.

4> seperation of ciliary body attachment to scleral spur- cyclodialysis

5> trabecular meshwork- trabecular meshwork tear

6> zonules - zonular dialysis

7> retinal attachment at ora serrata - retinal dialysis especially supero nasal